Conventionally, as a method of providing nanoimprint, optical element or the like with a fine shape, such a method has been adopted that the shape is transferred to a glass substrate, plastic substrate, plastic film, etc. using a mold with the fine shape beforehand formed therein (Patent Documents 1 and 2).
Among these techniques are a method of pressing a mold (also referred to as a die or a template) that is an original plate with a pattern of fine grooves, holes, etc. formed therein against a transfer target material and thereby transferring the pattern mechanically, another method of transferring using a thermoplastic resin, still another method of optically transferring using a photo-curing resin, etc. (Patent Document 3). The resolution of the pattern in these methods is determined by fabrication accuracy of the mold. In other words, once the mold is prepared, it is possible to form the fine structure with an inexpensive apparatus. As the mold that is the original plate, known generally are a parallel flat-plate type mold (referred to as a wafer or plate) and a cylindrical (roller) type mold, from their shapes (Patent Document 4, Non-patent Document 1).
As the parallel flat-plate type mold, there are a method of applying an ultraviolet light resist, electron beam resist, X-ray resist or the like onto a substrate using the semiconductor lithography technique, then irradiating and exposing the substrate with/to ultraviolet light, electron beams, X-rays or the like, and fabricating an original plate of a desired pattern, and another method of fabricating an original plate through a mask (reticle) with a pattern beforehand rendered therein (Patent Document 5).
Theses methods are very effective methods in case of an extremely fine pattern of about 100 nm on a flat plate. However, since a photoresist using photoreaction is used, it is necessary to expose using a spot smaller than the pattern required in principle so as to form a fine pattern. Accordingly, since a KrF or ArF laser, etc. with short wavelengths is used as an exposure light source, the exposure apparatus is large and the complicated mechanism is required. Further, in the case of using an exposure light source of electron beam, X-ray or the like, since a vacuum is required as an exposure atmosphere, it is necessary to place the original plate in a vacuum chamber. Therefore, it is significantly difficult to increase the original plate size. Meanwhile, to fabricate a large-area mold using these methods, considered is a method of using a step-and-repeat function for connecting small exposure areas to fabricate, but there is a problem with accuracy of connection between patterns (Patent Document 6).
Meanwhile, as the method of fabricating a cylindrical (roller) type mold, two methods have conventionally been adopted. First, there is a method of fabricating a parallel flat-plate original plate once, transferring the shape by electroforming comprised of a thin foil made of nickel or the like, and winding the thin foil around a roller (Patent Document 7). Another method (seamless roller mold) is to directly render a mold pattern on a roller by laser processing or mechanical processing (Non-patent Document 2). In the former method, it is necessary to wind a nickel thin-foil mold with an area larger than the area to manufacture, and there is another problem that a seam arises in the winding portion. Meanwhile, in the latter method, once the mold is fabricated, the mold is high in productivity and excellent in volume production, but it is significantly difficult to form a pattern of the submicron (less than 1 μm) size using laser processing or mechanical processing.
Further, as another problem of the roller mold, there is a problem that is difficult to control the depth of the fine structure. Conventionally, in the parallel flat-plate type mold, to control the ratio between the width and the depth i.e. the aspect ratio, applied is dry etching having anisotropy in etching. In this case, since a method is adopted of etching while placing the flat-plate shaped mold and counter electrode to oppose to each other so that the distance between an etched portion and the opposed counter electrode is always equal during the etching, the etching proceeds uniformly in the same direction inside the flat-plate mold surface. The etching depth is controlled using the dry etching apparatus of such apparatus design. However, since a seamless roller mold has the need of etching a curved surface, in the case of using an ordinary flat-plate shaped counter electrode, portions arise where the distance between the etching layer and the flat-plate shaped counter electrode is not equal, the etching direction and etching rate thereby vary in part on the curved surface, and it has previously been difficult to control the aspect ratio using such a method.
As only a previous method of forming a seamless roller mold with a pattern of the submicron (less than 1 μm) size, there is a method of using an anodized porous alumina (Patent Documents 8 and 9). In this method, formed is an anodized porous alumina layer having a regular arrangement of fine holes, and the concavo-convex shape corresponding to the arrangement of fine holes is formed on a roll-shaped mold. However, in this method, the formable fine shape is limited to regular fine-hole shapes of the same size, and the method has problems that it is not possible to form fine-hole shapes with various dimensions on the same roll, or to form groove shapes having rectangular or V-shaped concavo-convex shapes.    [Patent Document 1] U.S. Pat. No. 5,259,926    [Patent Document 2] U.S. Pat. No. 5,772,905    [Patent Document 3] Japanese Unexamined Patent Publication No. 2005-238719    [Patent Document 4] Japanese Unexamined Patent Publication No. 2006-5022    [Patent Document 5] Japanese Unexamined Patent Publication No. 2007-144995    [Patent Document 6] Japanese Unexamined Patent Publication No. 2007-258419    [Patent Document 7] Japanese Translation Unexamined Patent Publication No. 2007-507725    [Patent Document 8] Publication No. WO 2007-023960    [Patent Document 9] Japanese Unexamined Patent Publication No. 2008-229869    [Non-patent Document 1] Hua Tan, Andrew Gibertson, Stephen Y. Chou, “Roller nanoimprint lithography” J. Vac. Sci. Technol. B16(6), 3926 (1998)    [Non-patent Document 2] “Collection of nanoimprint application examples”, pages 611-612, published by JOHOKIKO Co., LTD.